Combustion engine systems are configured to operate at a determined power output and efficiency. Increasing the operational flexibility of a combustion engine can be achieved by varying the combustion engine's speed for any given power output. Varying the combustion engine's speed can include a starting means for initiating engine operation or a controlling means for operating the combustion engine in a running mode. Effectively varying the combustion engine's speed during a starting or running mode can result in decreased maintenance costs, improved starting performance, prolonged engine life, higher efficiencies, and fewer emissions.